1. Field of the Invention
The present invention generally relates to a method for intercepting input/output requests and responses in a proprietary operating environment or virtualization hypervisor utilizing open source or GNU Public License device drivers.
2. Description of the Related Art
Proprietary operating environments and virtualization hypervisors may not provide mechanisms to intercept input/output (“I/O”) requests for the purposes of adding functionality to or processing of the data in the I/O stream. It is highly advantageous for proprietary operating environments and virtualization hypervisors to utilize open source or Gnu Public License (GPL) device drivers.
The producers of proprietary operating systems, execution environments, and virtualization hypervisors often are reluctant to allow other companies to modify or add functionality within their core intellectual property and do not provide published/supported mechanisms to do so. It is desirable for independent software and hardware companies to add unique value to the I/O streams of these closed/proprietary environments in a manner that is minimally intrusive such that it introduces minimal chance for destabilization of the proprietary system, introduces minimal change to the closed/proprietary environment, and does not rely upon unpublished, proprietary, or likely to change mechanisms.
There are two primary prior art approaches that are commonly used to provide additional functionality to the I/O stream of a proprietary operating system. The first approach commonly used is development of specific device drivers for the proprietary system. In the case of common functionality that is to be added across all devices, all device drivers must be developed/modified to provide the desired functionality. This may be practical if the proprietary environment provides a driver development API or utilizes open source or GPL device drivers and there is a fixed small set of drivers affected. The second approach commonly used is reverse engineering and/or patching of the proprietary environment or device drivers. This approach is highly undesirable for technical (and in some cases legal) reasons. This approach is very prone to fail with new releases/version/patches/updates to the proprietary environment.
Computing environments often are very heterogeneous and contain hardware from many different manufacturers. This presents a considerable development and support burden for the developers and system administrators of operating systems, execution environments, and hypervisor-virtualization. The utilization of open source and GPL device drivers allows the producers of proprietary operating systems, execution environments, and virtualization hypervisors to avoid developing their own device drivers to support many types of hardware which their products will run on or are connect to.
In order to utilize open source or GPL device drivers, the proprietary environment is forced to freely provide source code of any modifications they make to the device drivers. The proprietary environment must also not statically link in the device drivers (otherwise they would be required to provide source code to their entire system), and finally must introduce a compatibility library that provides an interface between the proprietary system and the open source/GPL drivers that supplies all the supporting functionality required by the open source/GPL device drivers. Since this compatibility library contains portions of open source/GPL source code necessary to provide the required supporting functionality, it too must by dynamically linked and the source code for the compatibility library must be freely published.
The following definitions are used herein.
Hypervisor is a hardware virtualization technique that allows a computer to host multiple operating systems by providing a guest operating system with a virtual operating platform.
GNU, General Public License is a license for an open source operating system based on UNIX, which requires that derived works be distributed under the same license terms.
Kernel is a component of an operating system that connects a computer's software applications to the computer's hardware.
Application Programming Interface (API) is a collection of computer software code, usually a set of class definitions, that can perform a set of related complex tasks, but has a limited set of controls that may be manipulated by other software-code entities. The set of controls is deliberately limited for the sake of clarity and ease of use, so that programmers do not have to work with the detail contained within the given API itself.
Virtual Machine is a software abstraction of a physical computer.
Device driver is a software program that allows a hardware device to interact with software installed on the hardware device.
Function pointer is a programming language data type that invokes a function in a computer memory.
Virtualization allows a person to operate multiple virtual machines (computers) on a single physical machine (computer).
Compatibility library is a software program that provides an interface between computer programs, and in particular an interface that provides an interface between a proprietary environment and an open source or GNU GPL device driver that provides the supporting functionality for the device driver.